Proteins called prions are well known for causing fatal diseases in animals, such as Creutzfeldt-Jakob disease in humans and “mad cow disease” in cattle. New research published in PLOS Pathogens could help scientists uncover the mechanisms used by prions to infect animals.
Put simply, prions are a misfolded version of a normal protein found in healthy brains. When prions come into contact with other normal proteins of the same type, they can trigger them to misfold and become prions, too. As they build up, these misfolded proteins cause severe brain damage.
Like all proteins, prions consist of a long sequence of amino acid molecules. Previous research has shown that, under certain conditions, the amino acid sequence of a prion can change, or mutate.
In the new study, Ilaria Vanni of Italy’s National Institute of Health and her colleagues discovered that they had caused such a mutation while working with samples of prions that cause scrapie, a disease that afflicts sheep. They isolated the mutant and found that, like other prions, it was able to multiply in the lab outside of an animal.
To learn more about the mutant prion, the scientists tried to use it to infect small laboratory rodents called bank voles. They discovered that the mutant prion was unable to infect the rodents. In contrast, the natural, unmutated form of the prion was able to successfully infect the animals.
Looking deeper, the researchers determined the amino acid sequence of the mutant prion and found that it was missing a stretch of amino acids that is present in the unmutated form. In their new paper, they hypothesize that this missing segment is essential for animal infection, but not for multiplication in the lab.
In the future, further studies could build on these findings to pinpoint key features of prions that let them infect animals. This could aid understanding of these deadly proteins and potentially open up new directions for development of prevention and treatment strategies.
Citation: Vanni I, Migliore S, Cosseddu GM, Di Bari MA, Pirisinu L, D’Agostino C, et al. (2016) Isolation of a Defective Prion Mutant from Natural Scrapie. PLoS Pathog 12(11): e1006016. doi:10.1371/journal.ppat.1006016
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